This invention relates to a means to heat a molten metal pool which is taken out temporarily from a furnace into a ladle before being poured into a casting mold, and to a method of heating the molten metal pool with the heating means.
When a molten metal pool taken out temporarily from a convertor into a ladle and retained there is sent then, for example, to a continuous casting apparatus for the purpose of casting, the temperature of the molten metal pool tends to fall if it is retained in the ladle for a long time. The temperature fall is serious for casting technique whatever its amount may be. Thus, an approach to overcome this problem is called for.
The inventor of the present invention has tried to heat a molten metal pool with a flame of an oil burner blown towards the surface of the pool in order to settle this problem, i.e. to prevent the temperature of the pool in the ladle from falling. However, according to this method, it is a disadvantage in practice that most of the volume of the flame moves upwards without touching the surface of the molten metal pool, and heating efficiency at the surface of the pool is very low. The flame in this trial can be substituted by a plasma torch. The heating efficiency with a plasma torch as an alternative to the oil burner remains still low unless heat of the plasma torch is confined by a special construction enclosing it.
One object of the present invention is to provide a heating means which can heat a molten metal pool while it is retained in an usual ladle, and is very simple for treating a molten metal pool.
Another object of the present invention is to provide a heating means in which a molten metal pool contained in a large ladle can be heated conveniently by plural heating units immersed in the ladle and arranged closely to one another without causing mutual interference.
Still another object of the present invention is to provide a heating means in which a heating electric arc struck in a space surrounded by a hollow feeding electrode and the surface of the pool can transmit its heat to the molten metal pool with high thermal efficiency, i.e. with reduced heat loss.
Still another object of the present invention is to provide an effective heating method according to which the surface of the molten metal pool inside the hollow feeding electrode partly immersed in the pool is depressed lower than that outside the electrode by the pressure inside the electrode raised by the gas introduced there, and the elongated arc can transmit its heat with high efficiency to the whole pool through the enlarged internal side surface of the feeding electrode.